1. Field of the Invention
The present invention relates to an image pickup apparatus, an image display apparatus, and an image display system capable of preventing an image influenced by fluctuations in an output of a power source from being displayed.
2. Description of the Related Art
Hitherto, there is an image pickup apparatus for obtaining image data of a subject by photoelectrically converting an optical subject image formed by an optical system such as a lens. The image pickup apparatus generally has therein a solid-state imaging device such as a CCD or CMOS. The image pickup apparatus consumes power supplied from a predetermined power source, makes the solid-state imaging device perform the photoelectric converting process and, as a result, obtains an image of a subject. The image of the subject obtained by the image pickup apparatus is supplied to an image display apparatus or the like, and is displayed on a display.
Such image pickup apparatuses include an image pickup apparatus for correcting, for example, the black level of an image based on a signal level detected in an optical black region as a pixel region to which light from a lens is not always applied (refer to Japanese Patent Application Laid-open No. 2006-295346) and an image pickup apparatus for capturing an image of the inside of an organ of a subject (hereinbelow, also called an in-vivo image) by a solid-state imaging device provided in a capsule casing formed in a size which can be introduced into the organs of a subject (refer to Japanese Patent Application Laid-open No. 2003-70728). For example, there is also a solid-state imaging device built in such an image pickup apparatus, in which optical black regions are scattered about within an effective pixel region for generating an output signal of a captured image (refer to Japanese Patent Application Laid-open No. 2007-19820).
In an image pickup apparatus for capturing an image of a subject by consuming power from a predetermined power source as described above, there is a case that supply of power becomes insufficient due to fluctuations in output of the power source or exhaustion of a battery which is internally provided as the power source. As a result, fluctuations in the power source voltage supplied to an image pickup system such as a solid-state imaging device in the image pickup apparatus increase. Due to the fluctuations in the power source voltage, there is a case that an image of a subject captured by the image pickup apparatus is influenced. The influence on an image, of the fluctuations in the power source voltage varies according to the circuit configuration in an image pickup apparatus. For example, there is a case that the black reference level in an image is not uniform but is non-uniform in an entire display image due to such fluctuations in the power source voltage.
However, in the above-described conventional techniques, it is difficult to stop outputting image data influenced by fluctuations in the power source voltage of an image pickup apparatus in enormous image data captured by the image pickup apparatus, that is, image data influenced by fluctuations in the black reference level. There is, consequently, a problem that it is difficult to provide a stable image to the user without displaying an image influenced by fluctuations in the power source voltage of the image pickup apparatus.